When measuring the contrast of pixels of an LCD panel inspected using a CCD camera, it is important to detect pixels of an inspected LCD panel so that there are a small number of corresponding pixels on the detecting CCD in order to provide an inexpensive, accurate and suitable inspection system for use in a production line.
According to conventional methods, matching the positions of pixels on the LCD panel with pixels on the CCD camera is performed as follows:
1. A calibration pattern for matching the pixel position shown in FIG. 6 is displayed on the LCD panel as a luminescent spot; PA1 2. The contrast of the LCD pixels is measured by defining a unit, comprising multiple CCD pixels upon which the luminescent spot impinges, and setting the center CCD pixel of the unit to correspond to the center of the LCD pixel; PA1 3. The center positions of all of the LCD pixels are calculated and defined to correspond to the addresses of the CCD pixels using integer values (with reference to the addresses of the center pixels of the luminescent spots). PA1 4. The contrast detected by the CCD pixels corresponding to the center of each of the LCD pixels on the LCD panel is measured and the positions of the LCD pixels are defined to correspond to the positions of the CCD pixels based upon the results of this measurement. In order to specify the positions of the LCD pixels by the above-described method, a number of CCD pixels are defined to correspond to a single LCD pixel (for example, 36 CCD pixels correspond to a single LCD pixel).